Kick control for ultradeep boreholes has certain important distinguishing features from the kick control for more "normal" depth wells. The annular pressure profile vs. time is different in the two cases because the initial shut-in pressure in the ultradeep holes is large and sometimes it is the largest during constant bottomhole pressure (CBHP) kick control, resulting in small gas expansion effects. In shallow holes, the lower initial shut-in pressure and low pressure level (compared to ultradeep borehole annular pressures) throughout the kick control operation results in significant gas expansion. Therefore the annular pressure during the kick control may be substantially higher than the shut-in pressure. Thus, the critical period between the two cases happens at a decidedly different time. Kick simulation for ultradeep holes is presented in this paper for different CBHP methods using waterbase muds in any borehole geometry. The worst case, that of a sudden influx of a gas slug is used. The results are profiles of surface annular pressures, identifying the largest pressure value at each depth during the kick circulation with the CBHP methods. This allows the quantification of the load on a borehole during controlled CBHP kick-killing-operations at any depth.